Kocha alisema jezi zote zinapaswa kuwa safi kabla ya mechi ya kesho.

Alisema means he/she said.

It breaks down like this:

• a- = he/she
• -li- = past tense
• -sema = say

So Kocha alisema = The coach said or A coach said.

If it were plural, you would get walisema = they said.

In Swahili, the word kwamba = that is often optional after verbs like say.

So both of these are fine:

• Kocha alisema jezi zote zinapaswa kuwa safi...
• Kocha alisema kwamba jezi zote zinapaswa kuwa safi...

The second one is a little more explicit, but the first is completely natural.

Jezi is a borrowed noun, and like many borrowed nouns in Swahili, it often keeps the same form in both singular and plural.

So:

• jezi can mean jersey
• jezi can also mean jerseys

You know whether it is singular or plural from the agreement words around it.

In this sentence, it is clearly plural because of:

• zote = all for a plural class
• zinapaswa = they should / they are supposed to

So jezi zote must mean all jerseys.

This is noun class agreement.

Even though jezi itself does not change form, the words agreeing with it do change.

Here:

• zote agrees with plural jezi
• zi- in zinapaswa also agrees with plural jezi

So the sentence is showing plural agreement in two places.

A useful comparison:

• jezi yote inapaswa kuwa safi = the whole jersey should be clean or the jersey should be clean
• jezi zote zinapaswa kuwa safi = all jerseys should be clean

So yote / i- would point to singular, while zote / zi- points to plural.

Zinapaswa means something like:

• they should
• they are supposed to
• they are expected to
• they are required to

It is built like this:

• zi- = subject marker for plural jezi
• -na- = present tense
• -paswa = be supposed to / should

So jezi zote zinapaswa... literally means all jerseys are supposed to...

Because after -paswa, Swahili normally uses an infinitive verb.

Here:

• zinapaswa = they should / they are supposed to
• kuwa = to be
• safi = clean

So zinapaswa kuwa safi = they should be clean

You cannot normally leave out kuwa here.
So zinapaswa safi would not sound right.

Because safi is one of the adjectives that normally stays the same regardless of noun class.

So you can have:

• jezi safi
• nguo safi
• meza safi

The adjective does not need a class prefix here.

This is different from some other adjectives in Swahili that do change to match the noun class.

Kabla ya means before.

It is a common fixed expression:

• kabla ya mechi = before the match
• kabla ya kazi = before work
• kabla ya kula = before eating

So in your sentence:

• kabla ya mechi ya kesho = before tomorrow’s match

You should learn kabla ya as a set phrase.

Mechi ya kesho literally means match of tomorrow, which is how Swahili commonly says tomorrow’s match.

Here:

• mechi = match
• ya = a linking word meaning something like of
• kesho = tomorrow

So:

• mechi ya kesho = tomorrow’s match

This ya is very common in Swahili for linking nouns and noun-like words.

No. Swahili usually does not use articles like the or a/an.

So:

• kocha can mean the coach or a coach
• mechi can mean the match or a match

The exact meaning usually comes from context.

That is why Kocha alisema... can naturally be translated as either:

• The coach said...
• A coach said...

depending on the situation.

Yes. A very natural alternative would be:

• Kocha alisema jezi zote lazima ziwe safi kabla ya mechi ya kesho.

This also means The coach said all jerseys must/should be clean before tomorrow’s match.

The difference is roughly this:

• zinapaswa kuwa safi = should be clean / are supposed to be clean
• lazima ziwe safi = must be clean / definitely have to be clean

So lazima can sound stronger, while zinapaswa can sound a little more formal or softer, depending on context.

Yes. Swahili often allows time expressions to move around for emphasis.

For example, you could also say:

• Kabala ya mechi ya kesho, kocha alisema jezi zote zinapaswa kuwa safi.
• Kocha alisema kabla ya mechi ya kesho jezi zote zinapaswa kuwa safi.

But the original version is very natural and straightforward:

• Kocha alisema jezi zote zinapaswa kuwa safi kabla ya mechi ya kesho.

Putting the time phrase at the end is common and easy to follow.